1. Field of the Invention
This invention relates to an apparatus for applying surgical fasteners, and more particularly to an apparatus for resection, transection and creation of anastomoses.
2. Background of the Art
Surgical fastening apparatus for resection, transection and creation of anastomoses are used, for example, for suturing gastric and intestinal walls with spaced parallel rows of longitudinally aligned surgical fasteners or staples.
U.S. Pat. No. 3,079,606 to Bobrov et al. discloses an instrument for suturing gastric and intestinal walls with metal staples by inserting the tips of the instrument through apertures in the walls of the organs to be sutured. The apparatus includes a two part frame with each part having a finger-like projection or fork. The forks are inserted respectively into the apertures in the walls of the organs to be sutured. The frame parts are hinged together with the body tissue held between the forks. When the instrument is actuated, or "fired", longitudinally moving cam bars contact staple drive members in one of the forks, thereby pushing the surgical staples through the body tissue and into an anvil in the opposite fork by which they are crimped closed. A knife blade between the cam bars creates an incision between the parallel rows of staples. It should be noted, however, that the knife blade is an optional feature, i.e. the instrument may be used to fasten body tissue without creating an incision between the rows of staples.
U.S. Pat. No. 3,490,675 to Green et al. discloses an improvement on the instrument discussed above, whereby a double row of staples is placed on each side of the incision.
A further improvement in this type of instrument is disclosed in U.S. Pat. No. 3,499,591 to Green, which incorporates an improved structure for the staple carrying cartridge, the pusher assembly which includes the cam bars and the knife, and the staple drive members.
Generally, the above mentioned instruments are successfully used in abdominal, gynecological, pediatric and thoracic surgery. Surgical fastener applying apparatus can be used to apply metal staples, which are crimped in the anvil portion of the apparatus, or bioabsorbable fasteners, such as two-part fasteners having a fastener portion and a retainer which interlocks therewith upon firing of the instrument.
In any such instrument it is important to maintain proper alignment: alignment of the jaws of the instrument, and alignment of the tissue held between the jaws. Alignment of the instrument insures that the surgical fasteners are properly closed to achieve hemostasis. In the case of metal staples, the staples are closed when their legs are crimped in corresponding depressions, or "buckets", in the anvil. The staples are typically less than 1/10" across. Misalignment between the staple legs and buckets can cause faulty crimping of the legs. Without proper closure of the staples the body tissue may be improperly sealed, possibly resulting in bleeding, infection, and added trauma.
Forces encountered during the stapling operation can contribute to misalignment. For example, if the tissue being operated upon is wedge shaped, with one side being thicker than the other, the stapler jaws will have a tendency to "roll". Deflection can also occur as a result of vertical forces applied to the anvil during contact by the fasteners. More deflection occurs at the distal end of the anvil. The longer the anvil the greater the tendency to bend. Hence, one way of dealing with bending is to limit the length of the anvil. But in many applications it is desirable to use a longer anvil, which would be able to apply longer rows of staples.
Another way of reducing bending is to make the anvil stronger. Anvils are presently fabricated by cold working sheet stainless steel of about 0.05 inches to about 0.075 inches in thickness into the desired shape. Stronger anvils can be made by increasing the thickness of the steel. However, this presents disadvantages insofar as the weight and cost of the anvil, as well as the difficulty of working thicker steel. Using an alternative harder material of construction can increase the rigidity of the anvil, but possibly at the expense of sacrificing desirable properties of the stainless steel.
Thus, alignment is affected by close mating of the parts of the apparatus, precision of the geometry of the parts, and the strength and design of the parts. An example of a surgical staplers designed to maintain alignment of tissue is disclosed in U.S. Pat. No. 5,014,899. Examples of surgical staplers designed to maintain alignment of the jaws are in U.S. Pat. Nos. 4,863,088 and 5,405,072. In particular, U.S. Pat. No. 5,405,072 discloses an anvil having lengthwise indentations on the side walls of the anvil to increase resistance to bending. U.S. Pat. No. 4,863,088 discloses a stapler having a support element 60 which engages a socket 66 in the opposing jaw part to restrict deflection of the handle parts and limit transverse deflection of the jaw parts relative to each other. The present application is directed to a surgical stapler which incorporates an alternate approach to maintaining alignment of the jaws.